hot to add shortcode in wordpress code example

Example 1: wordpress shortcode

function wp_demo_shortcode() { 

//Turn on output buffering
ob_start();
$code = 'Hello World';
ob_get_clean();

 // Output needs to be return
return $code;
} 

// register shortcode
add_shortcode('helloworld', 'wp_demo_shortcode');

Example 2: wordpress create shortcode

// function that runs when shortcode is called
function wpb_demo_shortcode() { 
 
// Things that you want to do. 
$message = 'Hello world!'; 
 
// Output needs to be return
return $message;
} 
// register shortcode
add_shortcode('greeting', 'wpb_demo_shortcode');